Nongaseous pyrotechnic delay mixture



March 7, 1961 R. H. COMYN NONGASEOUS PYROTECHNIC DELAY MIXTURE FiledJuly 13, 1950 RAYMOND R-MMJM H. COMYN Patented Mar. 7, 1961 NONGASEOUSPYROTECHNIC DELAY MIXTURE Raymond H. Comyn, 316 Southampton Drive,Northwest Park Apts., Silver Spring, Md.

Filed July 13, 1950, Ser. No. 173,636

1 Claim. (Cl. 52-2) (Granted under Title 35, U.S. Code (1952), see. 266)This invention relates to a nongaseous delay pyrotechnic mixture for usein a projectile, rocket, flare, smoke float, or any other ordnancemissile or device and is particularly adapted to cause initiation of theexplosive or propellent charge, light or smoke emitting pyrotechnicmixture, as the case may be, in time delayed relation with respect tothe initial ignition thereof by the usual igniter associated therewith.

Heretofore, gasless delay compositions used in ordnance missiles anddevices by the armed forces for delaying the ignition of the pyrotechnicmixtures or explosives therein such, for example, as a bursting charge,propellent charge, light or smoke emitting composition as the case maybe, have not been altogether satisfactory for the reasons that suchcompositions were susceptible to changes in gas pressure and thus theburning range thereof was affected by the gas pressure producedtherefrom during ignition and burning of such compositions therebycausing erratic burning rate thereof. Further! more, such compositionslack stability, in that they would absorb sufiicient moisture to reducethe efiiciency and effect the burning rate thereof and upon numerousoccasions fail to function altogether at low temperature particularlyafter being stored over a long period of time. Such compositions alsoproved not altogether satisfactory for the purpose intended inasmuch asthe burning rate was erratic and unpredictable and the ignitionsensitivity characteristic thereof was nonuniform.

The present invention is especially compounded to overcome the aforesaidobjections found in prior art compositions and to provide a new andimproved nongaseous delay mixture having the admirable charac- 'teristicof stability, sensitivity and uniform burning rate without noticeablegas evolution therefrom.

An object of this invention is to provide a new and improved nongaseousdelay mixture for use in an ordnance missile which forms solidconbustion products, and does not evolve an appreciable amount of gasduring burning thereof.

Another object of the invention is to provide a stable nongaseous delaymixture having an ignition temperature lower than the burningtemperature of the igniter associated therewith and which is ignited bythe igniter whereupon the burning range of the mixture is unaffected bythe gas pressure produced during the burning thereof.

Another object of the invention is to provide a sensitive nongaseousdelay mixture whose burning rate is predictable, and which producessufiicient heat at a high temperature to ignite either a detonator or arelay igniter, as the case may be.

An additional object is to provide a method of producing a nongaseouspyrotechnic delay mixture.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawing wherein:

One adaptation of the invention is illustrated in the accompanyingdrawing which is a fragmentary longitudinal sectional view of anordnance device.

The missile comprises the usual shell or casing 10 having a normallylocked firing pin 11 adapted to be moved to a firing position inengagement with the primer 12 upon impact of the missile with a target,it being understood, however, that the firing pin is released formovement to the firing position when the detents 13 are moved out ofengagement therewith by centrifugal force as the missile travels along atrajectory. Arranged with,- in the cavity 14 formed in the shell 10 andhaving an igniter 15 on one end, and an igniter 16 on the other endthereof is the nongaseous delay mixture 17 of the present invention, theigniter 15 being adapted to be ignited by the primer 12 when the firingpin is moved to the firing position, whereupon the delay mixture isignited by the igniter l5 and will burn at a predetermined rate, withoutnoticeable gas evolution therefrom for a predetermined period of timesuch, for example, as from 3.83 to 4.05 seconds whereupon the igniter 16is ignited by the delay mixture and thus the booster charge 18 is firedin time delayed relation with respect to impact of the missile with thetarget thereby firing the bursting charge and exploding the missile.

The composition of the present invention possesses the characteristicswhich make it admirably suited for the uses indicated herein andcomprises a mixture of cobalt as a metallic fuel, lead chromate andpotassium perchlorate as a pair of oxidizing agents. The cobalt inpowder form is treated first with a hot aqueous solution of potassiumdichromate and then With a carbon tetrachloride solution of stearic acidprior to the mixing of the cobalt with the lead chromate and potassiumperchlorate. This is done to protect the cobalt from deterioration.

A typical mixture producing satisfactory stability, sensitivity, burningrate and showing no appreciable gas evolution while burning is asfollows:

Percent Cobalt 41 Lead Chromate 47 Potassium perchlorate 12 It will beunderstood, however, that the proportions of these ingredients may bevaried, if desired, to meet the requirements of various uses of themixture.

The mixing of the ingredients may be accomplished in any suitable mannerand during such mixing operation carbon tetrachloride may be added toreduce particle friction of the ingredients to a sufiiciently low valueto facilitate mixing.

Both wet and dry methods of mixing the ingredients have been tested andfrom such tests it has been found that while both methods aresatisfactory the dry method of mixing in certain cases is mostsuccessful and has produced the best results. Furthermore, when the drymethod is employed it does not require drying and regrinding aftermixing as is the case when employing the aforesaid wet method. Inpreparing the ingredients comprising the nongaseous delay mixture of theinstant invention it has been found that the most satisfactory resultsare obtained when the cobalt is of a particle size such, for example, asless than the U.S. standard sieve, mesh size 325/000, the lead chromateis of such a particle size as to readily pass through a U.S. standardsieve, mesh size 200/000, and the potassium perchlorate of such aparticle size as to pass through a U.S. standard sieve, mesh size325/000. When the aforesaid preparation has been completed theingredients are then thoroughly mixed in any suitable manner butpreferably by placing them in a mixing device, the device being of anytype suitable for the purpose such, for example, as the type known inthe trade as the Simpson mixer. During the mixing operation a quantityof carbon tetrachloride may be added to the ingredients, if desired,thereby reducing the friction between the particles thereof and alsoinsure thorough mixing of the ingredients. The time period required tomix the aforesaid ingredients thoroughly when the mixer is set inoperation is approximately 30 minutes, the ingredients being subjectedto a mulling action as the mixer operates.

It has been found that ingredients comprising mixtures of this type maysegregate during wet mixing with the lighter materials coming to thetop, and it is probable that this condition may also occur during drymixing of the ingredients and thus this eifect can be minimized byemploying chemicals as heretofore described, with densities and particlesizes which are approximately in the same range. Furthermore, it hasbeen found that mixing is improved by employing as few chemicals aspossible, such, for example, as disclosed in the instant invention,rather than four or five chemicals, as heretofore used in prior artdevices.

It will be understood, however, that as either the metallic fuel or theoxidant in a mixture is increased over the amount necessary for maximumheat, the reaction heat measured in calories per gram, will decrease.Under some conditions an excess of metallic fuel may be undesirable;while an excess of oxidant may tend to decrease the burning rate of themixture. However, a large excess of an oxidant may be undesirable if theoxidant releases its oxidizing element very easily.

The use of an inert diluent provides another method of reducing thereaction heat and the burning rate of the mixture. However, there is thepossibility of actually stopping the whole reaction if the mixture isuneven. By the addition of a second oxidant, as heretofore described,which reacts with the fuel at a slower rate than the first oxidantthereby providing an effective method of slowing the burning rate of themixture, and thus as long as the fuel and both of the oxidants arepresent in stoichiometric proportions, the danger of bubbles due to asudden excess of oxygen being released by the oxidant is decreasedwhereupon uniform and complete burning of the mixture is insured.

It is well known in the art of delay mixtures that moisture acceleratesthe deterioration of gasless delay mixtures, such conditions resultingfrom the reaction of the ingredients of the mixture with moisture aswell as from ionic reactions which are promoted by the solvent action ofthe moisture. In view of these conditions existing in prior art mixturesthe instant invention overcomes such conditions by providing a mixturehaving the desirable characteristics of low water solubility; free fromhydrate formation, and not subjected to decomposition in water.

The particle size of the oxidant does not affect the properties of agasless delay element as much as the particle size of the fuel. As theparticle size decreases and the surface thereof increases, accelerationof the burning rate of the gasless delay element and surveillancedeterioration thereof may be expected. However,

it is desirable to use a fuel whose particle size lies in the subsieverange for the reason that they ignite more readily as the sizedecreases.

During tests, the gasless delay mixture and the starter and relayigniter compositions therefor were loaded in a steel test body atpressures from 10,000 to 35,000 p.s.i., the delay element being composedof three equal increments and disposed between the aforesaid igniters.The exposed top portion of the starter composition was ignited by anyconvenient means, whereupon the delay element proved to be sufficientlysensitive to be ignited by the starter igniter, the time required forthe delay element to burn to the bottom was substantially 4.05 seconds,the burning temperature thereof being sufiiciently high to causeignition of the relay igniter. Furthermore, the test proved that thegasless delay mixture burned evenly and at a relatively slow rate whenignited, without noticeable gas evolution therefrom.

In loading the gasless delay mixture into the delay cavity of anordnance missile or device it has been found that the best results wereobtained when the aforesaid increments were pressed into the cavity at apressure of 10,000 to 35,000 psi.

From the foregoing, it will be understood, that a gasless delay mixturefor an ordnance missile or device has been compounded either by wet ordry mixing methods disclosed herein and having new and improvedcharacteristics such, for example, as uniform mixing and surveillancequalities; whose burning range is unaffected by the gas pressureproduced during burning thereby permitting the delay mixture to burnevenly until entirely consumed;v and which is sufiiciently sensitive tobe ignited by the starter igniter and to furnish suflicient heat at ahigh enough temperature to ignite either a relay igniter or a detonator,as the case may be, and which will not evolve an appreciable amount ofgas during burning thereof.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

The method of producing a nongaseous pyrotechnic delay mixture whichcomprises the steps of first treating a quantity of powdered cobalt witha hot aqueous solution of potassium dichromate and thereafter treatingthe cobalt with a carbon tetrachloride solution of stearic acid, andmixing the treated cobalt with quantities of lead chromate and potassiumperchlorate.

References Cited in the file of this patent UNITED STATES PATENTS

